Device for varying the blood temperature



Sept. 3, 1968 E H. WALZ DEvIcE FOR VARYING THE BLOOD TEMPERATURE Filed Jan. 51. 1967 2 Sheets-Shet 1 Sept. 3, 1968 H. WALZ DEVICE FOR VARYING THE BLOOD TEMPERATURE Filed Jan. 51. 1967 2 Sheets-Sheet 2 fill/11A! Fig; 5

.Unird State Farm My r; 7:. I: 1 I DEVICE FOR VARYING'THE BLOOD TEMPERATURE Heinz Walz,Erlangen-,Germany, assignor to. Siemens Aktiengesellschaft, a corporation of. Germany. Filed Jan. 31,1967, ser. N 612,849 Claims priority, application Germany, Feb. 2 1966,

Arism'er har s mscrbs'uiie -'I-he blood' tem-perature varying "device has-"abandshaped flow-through space extending across substantially the entire s'urface'on one 'side' of -a'Peltier'block. The space has a width manytimes greater than-the thickness thereof and is provided with an inlet and an outlet "at the extremities thereof. The-space has fan-shaped transition portions "respectively outwardly flaring from and inwardly narrowing to the inlet and outlet andiscurved substantially in accordance with the stream lines of blood I flowing through the space. Furthermore, the spaceis defined by smoothly polished surfaces.

1 My invention relates to device for varying the 'blood temperature and more particularly a device of; that type which employs a Peltier block connected on the warm side thereof with cooling 'fins' and onjth'e cold side there 'gfwitha flow-through cooler actingas a heat. exchanger, both thecooling fins andthe flow-through cooler being thermally conductive with and electrically insulated from the Peltier block. v

Modern-surgical operating practice has sought for a long itime' to carry out anl operation underhypothermal conditions wherein the. temperature of the field of the operation is lowered toa v lue bel wjgso1o Under-such subcooled'cond ition, the ox gen, Iequirement'and this me ho i 'oi all tisf u fi s re u t ai aq a ex en and ;-the supply, of oxygenfto the e'sl Consequently rcfn'g no m-3 .3 m 'adt fi-lr j rrb uc L ofsubcooling in the lieldlof the operation, it has already been known to reducethe tempef'ature of the entire body, For this purpose, thebody i'sf 'cooled" from the eitterior thereof with ice packs, coolant" coils or coolingmats J traversed by a cooling liquid. By these means, subcooling to 15to20 'Q.. ha's been effected. Thejmost critical phase forfth is treatment s jthe'rjeyv ming of lthebody. The possibility of 'par'tial residual amag'e 'to 'the body or of fatal termin'ation Qf f the"pperation cannot be excluded. This'disadvantage c zbul d' greatly avoided if it were not" necessary to "subcoolftlieferitire body to the suh cooled temperatureldesired for thei fiel d of the operation. It would be ne.cessary',in' this regard,' to,f,have a cooling capability effective only in that portion of the blood circulating system with which ,the field of the operation is provided. subcooling can be achieved thereby that is effectiveonly in' the field of the operation and by means of which the metabolism of the organ on which the operation is to be performed can be reduced. At most, the temperature of the entire body is thereby reduced only a few degrees since only a small quantity of'cooled blood is required. t H .--The modification of the blood in an extracorporeal circulation system is. already.known from the heart-lung machine. For the problem aforementioned herein, the entireblood circulation system does not, however, have to be treated or modified. An extracorporeal circulation .system ,or loop portion has to be provided by means of which blood is tapped only from the artery-supplying the 3,399,536 Patented Sept.' 3 1968 fieldof the operation and, after being cooled, is re turned'to this artery. A flow-through cooler which is connected 'intothe extracorporeal portion of the circulation system presents itself as a suitable't'echnical solution of this problem. From the medical point of view, several technicalrequirements must be imposed upon these flowthroug'h coolers. The flow through the'cooler must take place without any congestion or obstruction in blind corners' thereof, in order to prevent coagulat'ion of-the blood. Microscopically. small, sharp irregularities in the surface of the'fiow-through space'are to be avoided so thatno damage can occur mechanically to the constituents of the blood. Further-more, the blood temperature must be maintained as constant as possible after the blood has passed the cooler flow-th'rough stage. Therefore, the occurrence of temperature gradients within the flow 'as it'passes through the cooling stage must be avoided as much as possible. "In addition, the flow-through space in the cooler must be well scaled to prevent the occurrence of interchange processes between the blood and the surroundings. The material from which the flow-through cooler is made must be corrosion-resistant, capable of sterilization and boilable. 7

These requirements cannot be met by cooling the flowthrough passage of the blood with water or any other liquid. Due to the limited heat exchange with such liquid coolants, a long cooling coil must be employed for the blood, and the formation of congested or obstructed locations and consequent coagulation of the blood is accordingly unable to be prevented therein. Also, when using a Peltier block for cooling the flow-through fluid, all of the aforementioned requirements can be met only if specific technical measures have been taken into consideration. In a Peltier block, many thermoelectric elements are combined so that the cold and the warm soldering locations thereof lie in one plane, respectively, namely the cold or warm side of the Peltier block. A liquid can be cooled in a flow-through space which is connected with the cold side of the block. However, to cool blood, the flow-through space must be of such construction that it meets the aforementioned conditions for avoiding the coagulation thereof.

It is accordingly an object of my invention to provide a device for varying the blood temperature which avoids the aforementioned disadvantages. More particularly, objects of my invention are to provide such a device as will avoid the possibility of obstruction of the blood and resulting coagulation thereof. r

With the foregoing and other objects in view, I provide in accordance with my invention a device for varying the blood temperature which comprises means having a flowthrough space extending in the shape of a band across substantially the entire surface on one side of a Peltier block and having a width many times greater than the thickness thereof and an outlet from and an' inlet to the flow-through space. The flow-through space has 'a fanshaped transition portion respectively flaring" outwardly from the inlet and narrowing toward the outlet. The transition portion is curved substantially in accordance with the stream lines of blood flowing through the space. Also, the spaceis defined by surfaces that are smoothly polished. I

In accordance with a further feature of my invention the cooled blood flowing back from the field of the operation or at least a portion thereof is conducted into a second extracorporeal circulating system adjacent the warm side of the block so as to reheat it at that location. The temperature of the entire body thus remains practically independent of the subcooling of the field of the operation. Consequently, in accordance with this further feature of my invention, there is provided a second heat exchanger, with a flow-through space having the aforementioned features, at the warm side of the Peltier block, in the place of at least part of the cooling fins, for heating the blood.- 1

Other features of my invention are that the heat exchangers are made of corrosion-resistant metal; furthermore, the flow-through space in each heat exchanger is sealed by means of a sealing member or gasket resistant to boiling, and the heat exchangers are removable. Also in accordance with a feature of my invention, I provide a regulating device which assures a specific constant temperature of the blood after it has passed through the flowthrough stage.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in device for varying the blood temperature, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic longitudinal view partly in section of an embodiment of the device for varying the blood temperature constructed in accordance with my invention;

FIG. 2 is a plan view of FIG. 1 with the cover plate on the right-hand side of FIG. I removed;

FIG. 3 is another diagrammatic longitudinal sectional view of a second embodiment of the device of FIG. 1;

FIG. 4 is a diagrammatic view of an extracorporeal portion of a blood circulating system in which the device of my invention is connected; and

FIG. 5 is a diagrammatic view of two extracorporeal portions of'circulating systems in which my device is connected.

In the hereinafter described embodiments approximately' one-half liter of blood per minute is cooled to C., and with the second embodiment shown in FIG. 3, the same quantity of blood that is thus cooled is again heated to body temperature.

Referring now to the drawings and first particularly to FIGS. 1 and 2 thereof, there is shown a Peltier block formed of pand n-conductive semiconductor members 1, contact bridges 2 therebetween and heat exchanger plates 3. Cooling fins 10 are superimposed on the heat exchanger plate 3 at the'warm side of the Peltier block and are ventilated by a fan 11 to remove the heat therefrom. A heat exchanger 4 is mounted on the heat-exchanger plate 3 at the 'cold side of the Peltier block and is provided with a flow-through space 6 that is closed by a cover plate 5, suitably secured thereon. The flow-through space 6 is provided with an inlet opening 7 and an outlet opening 8 at the extremities thereof. The flow-through space is sealed by a gasket 9. In the plan view of FIG. 2, the heat exchanger of FIG. 1 is shown with the cover 5 removed.

From both FIGS. 1 and 2 it is seen that dead or blind corners in the flow path of the blood, which might tend to cause congestion or stagnation of the blood, are avoided due to the band-shaped structure of the flowthrough space, owing to the rounding or curving of the corners thereof and due to the fan-shaped widening or broadening of the flow-through space adjacent the inlet and outlet openings 7 and 8 respectively. Due to the planar or flat shape of the flow-through space 6, the production of a temperature gradient transverse to the flow direction is, furthermore, prevented.

In the second embodiment of FIG. 3, the cooling fins 10 of the embodiment of FIG. 1 are replaced by a second heat exchanger. The second heat exchanger comprises a main plate 4,, a flow-through space 6', an inlet and an outletopening 7' and 8' respectively, and a cover plate 5' substantially of the same construction and function as the corresponding members of the first-mentioned heat exchanger of the embodiment of FIG. 1. A plan view of the heat exchanger shown on the left-hand side of FIG. 3, when the cover 5 thereof is removed, substantially corresponds to the plan view shown in FIG. 2.

FIG. 4 schematically shows an extracorporeal portion of ablood circulation system in which the device of my invention is inserted. It is to be assumed that the field of the operation is supplied through the artery 10. The artery 10 is interrupted at a location 13 and the blood from the artery 10 is conducted through a bypass tube 11 to the device 12 for cooling the blood. The bypass tube 11 can be made of suitable plastic material. The device 12 of my invention for cooling the blood corresponds to the device shown in greater detail in-FIGS. 1 and 2 and described hereinbefore. The blood flows from the portion of the artery 10, located at the left-hand side of FIG. 4, through the band-shaped flow-through space of the cooling device 12 and is returned to the artery 10 portion at the right-hand side of FIG. '4. In the field of the oper-j ation, a temperature reduction to about 15 C. is obtained thereby.

In FIG. 5, there are shown two extracorporeal portions of a blood circulating system. The first portion of the blood circulating system is tapped with the bypass tube 11 from the artery 10 which supplies the field 15,- having the capillary vessels 16, :wherein the surgical operation is to be performed. In this external portion 11 of the circulating system, there is again inserted a device 14 constructed in accordance with my invention for cooling the blood. The device 14 corresponds to the embodiment shown in FIG. 3 in detail, wherein a second flow-through cooler or heat exchanger for reheating the blood is superposed on the warm side of the Peltier block. By means of this second flow-through cooler, the blood is conducted through a bypass tube 18 out of a portion of a vein 17 which is broken at a location 19, and is returned after flowing through the device 14 to the vein 17 at the righthand side of FIG. 5. In the second heat exchanger of the device 4, the blood flowing back from the field of the operation or at least a portion thereof is reheated before it is returned to the circulation system proper of the body. The occurrence of damage to the entire organism due to subcooling of a field of an operation need no longer be feared when using this device of my invention.

Iciaim:

1. Device for varying blood temperature comprising a Peltier block having a warm side and a cold side, a flow-through heat exchanger connected to one of said sides of'said Peltier block in thermal conduction therewith and electrically insulated therefrom, said heat exchanger having a flow-through space traversible .by a flow of blood, said space extending band-shaped over substantially,the entire area of the Peltier block on one of. said sides thereof and having a width many times greater than the thickness thereof, and a blood inlet to and outlet from said flow-through space located at extremities thereof, said space being defined by smoothly polished surfaces and having fan-shaped transition portions respectively flaring from said inlet and narrowing to said outlet, said flow-through space having corners that are all rounded in outline, and said fan-shaped portions being defined by lateral surface at the flaring sides thereof having a given degree of inclination cooperating with said rounded corners for avoiding stagnation of blood flowing through said space.

2. Blood-temperature varying device according to claim 1, wherein said flow-through heat exchanger is connected to said cold side of said Peltier block, and cooling fins are connected to the warm side of said Peltier block in heat conductive and electrically insulating contact therewith.

3. Blood-temperature varying device according to claim 1, wherein said heat exchanger is formed of corrosion-resistant metal.

4. Blood-temperature varying device according to claim 1, wherein said flow-through space of said heat exchanger is sealed by a gasket resistant to boiling.

5. Blood-temperature varying device according to claim 1 including a second flow-through heat exchanger substantially similar to said first-mentioned heat exchanger and being similarly connected to the other side of said Peltier block.

6. Blood-temperature varying device according to able.

References Cited UNITED STATES PATENTS Nichols 165--170 Rich 62-3 Kistler 623 Ryan 62-3 Hirschhorn 623 Gonzalez 62-3 WILLIAM I WYE, Primary Examiner. 

